Technical Field
Embodiments described herein relate to the field of signal processing and more particularly, to implementing a low power decimator.
Description of the Related Art
Mobile phone handsets typically include a microphone that converts input sound pressure waves into an output electrical audio signal. The electrical audio signal is sampled and then typically processed and stored by the handset. Other devices also include microphones for capturing sounds, and these devices also include circuitry for performing various types of digital signal processing on the captured sounds.
The circuitry for processing digital signals often includes decimators, filters, and/or other types of signal processing logic. A decimator may be configured to decimate received input samples from oversampled bitstreams. As used herein, the term “decimate” may be defined as reducing the sampling rate of a signal. Decimation may include, or be accompanied by, filtering to mitigate aliasing distortion. In one embodiment, a decimator may utilize a finite impulse response (FIR) filter to filter the input samples. The equation for a general FIR filter is:
      y    ⁡          [      n      ]        =            ∑              i        =        0                    N        -        1              ⁢                  ⁢                  x        ⁡                  [                      n            -            i                    ]                    *              C        ⁡                  [          i          ]                    where N is the filter length, x[n−i] are the samples, and C[i] are the coefficients. However, if only one out of every M FIR filter results is needed, effectively applying 1/M decimation, the equation will be:
      y    ⁡          [      n      ]        =            ∑              i        =        0                    N        -        1              ⁢                  ⁢                  x        ⁡                  [                      Mn            -            i                    ]                    *              C        ⁡                  [          i          ]                    
With mobile and other devices running on battery power, techniques for reducing power consumption of the various signal processing circuitry (e.g., decimators) in the devices are desirable.